Interactive input systems that allow users to inject input (e.g., digital ink, mouse events etc.) into an application program using an active pointer (e.g., a pointer that emits light, sound or other signal), a passive pointer (e.g., a finger, cylinder or other suitable object) or other suitable input device such as for example, a mouse or trackball, are known. These interactive input systems include but are not limited to: touch systems comprising touch panels employing analog resistive or machine vision technology to register pointer input such as those disclosed in U.S. Pat. Nos. 5,448,263; 6,141,000; 6,337,681; 6,747,636; 6,803,906; 7,232,986; 7,236,162; and 7,274,356 assigned to SMART Technologies ULC of Calgary, Alberta, Canada, assignee of the subject application, the entire disclosures of which are incorporated by reference; touch systems comprising touch panels employing electromagnetic, capacitive, acoustic or other technologies to register pointer input; tablet and laptop personal computers (PCs); personal digital assistants (PDAs) and other handheld devices; and other similar devices.
Above-incorporated U.S. Pat. No. 6,803,906 to Morrison, et al. discloses a touch system that employs machine vision to detect pointer interaction with a touch surface on which a computer-generated image is presented. A rectangular bezel or frame surrounds the touch surface and supports imaging devices in the form of digital cameras at its corners. The digital cameras have overlapping fields of view that encompass and look generally across the touch surface. The digital cameras acquire images looking across the touch surface from different vantages and generate image data. Image data acquired by the digital cameras is processed by on-board digital signal processors to determine if a pointer exists in the captured image data. When it is determined that a pointer exists in the captured image data, the digital signal processors convey pointer characteristic data to a master controller, which in turn processes the pointer characteristic data to determine the location of the pointer in (x,y) coordinates relative to the touch surface using triangulation. The pointer coordinates are conveyed to a computer executing one or more application programs. The computer uses the pointer coordinates to update the computer-generated image that is presented on the touch surface. Pointer contacts on the touch surface can therefore be recorded as writing or drawing or used to control execution of application programs executed by the computer.
Multi-touch interactive input systems that receive and process input from multiple pointers are also known. One such type of multi-touch interactive input system exploits the well-known optical phenomenon of frustrated total internal reflection (FTIR). According to the general principles of FTIR, the total internal reflection (TIR) of light traveling through an optical waveguide is frustrated when an object such as a pointer touches the waveguide surface, due to a change in the index of refraction of the waveguide, causing some light to escape from the waveguide at the touch point. The multi-touch interactive input system employs machine vision to capture images including the light that escapes the waveguide at each touch point, and processes the images to identify the position of the pointers relative to the waveguide surface based on the escaped light.
U.S. Patent Application Publication No. 2011/0050650 to McGibney, et al., assigned to SMART Technologies ULC, discloses an interactive input system with improved signal-to noise ratio and image capture method. The interactive input system comprises an optical waveguide associated with a display having a top surface with a diffuser for displaying images projected by a projector and also for contact by an object, such as a finger. The interactive input system also includes two light sources. Light from a first light source is coupled into the optical waveguide and undergoes total internal reflection within the waveguide. Light from a second light source is directed towards a back surface of the waveguide opposite to its top surface. At least one imaging device, such as a camera, has a field of view looking at the back surface of the waveguide and captures image frames in a sequence with the first light source and the second light source on and off alternately. Pointer interactions with the top surface of the waveguide can be recorded as handwriting or drawing to control execution of an application program.
U.S. Patent Application Publication No. 2008/0179507 to Han discloses a multi-touch sensing display system employing a liquid crystal display (LCD) panel disposed between an optical waveguide and an imaging sensor. The LCD panel is adapted/designed to be transparent to infrared light so that infrared light injected into the optical waveguide by an LED light source escapes the optical waveguide and is imaged by the imaging sensor. Contacts on the optical waveguide can be detected.
U.S. Patent Application Publication No. 2008/0150913 to Bell discloses an interactive video display system including a transparent flat LCD panel beneath a transparent pane, a camera under the LCD panel and an illuminator that illuminates the transparent pane. The LCD panel is at least partially transparent to light visible to the camera. When an object is touching the transparent pane, light in the transparent pane is able to scatter, allowing it to escape the confines of the transparent pane. Interaction of the object with the touch surface of the transparent pane is then able to be detected by the camera under the LCD panel.
U.S. Patent Application Publication No. 2009/0219253 to Izadi, et al. discloses an interactive surface computer including an LCD panel with a switchable diffuser. The switchable diffuser replaces the typical fixed diffuser layer of the LCD panel and has two states, namely a transparent state and a diffusing state. When the switchable diffuser is in the diffusing state, IR sensors beneath the LCD panel can detect objects which are very close to the touch surface. When the switchable diffuser is in the transparent state, objects which are at a greater distance from the touch surface can be detected by another imaging sensor.
Although LCD panels have been employed in FTIR touch technology, improvements are desired. It is therefore an object of the present invention to provide a novel interactive input system and panel therefor.